1. Field of the Invention
The present invention relates to an ink, particularly to an ultraviolet ray-curable ink for printing.
2. Related Art Statement
Hitherto, many types of ultraviolet ray-curable ink are known, comprising a photo oligomer, a reactive diluent monomer, a photo initiator, a photosensitizer, a pigment, a pigment dispersant, and optional ink properties-imparting agents, such as a flow adjuster, a defoamer, and a levelling agent. However, the known inks have the following drawbacks.
When the inks are cured by irradiation with an ultraviolet ray, they suffer from cure shrinkages, so that adhesions of the inks to the adhered substances are deteriorated or lost. Even when the adhesions of the inks to the adhered substances are good, the adhered substances are frequently deformed due to handling, so that the cured inks become devoid of followability to the adhered substances, and bear an aging crack or cracks upon standing, only a small impact or bending force is exerted thereon.